In order to discuss improving effect of ecological forest on heavy saline-alkali soil and to provide reference for biological improvement of saline-alkali soil, the soil chemical properties (pH, salt content, organic matter, available potassium and cation exchange capacity) of 20cm-depth in four different stages of growth on pure forest of Fraxinus velutina planted on heavy saline-alkali soil were studied. The results showed that pH value of forest soil in other stages of growth except defoliating stage was lower than that of CK, pH value in flowering stage decreased by 0.77 unit, and the decrease was the largest. The organic matter obviously increased in four different stages of growth, but the best effect of soil organic matter improvement was defoliating stage. During defoliating stage in mid-October, salt content of forest soil was 1/2 of CK, and cation exchange capacity was three point two nine times of CK. The available potassium of forest soil obviously increased in flowering stage and peak leafing stage. All in all, there was greater effect for the soil chemical properties of 20cm-depth in different growth stages of pure forest of Fraxinus velutina, so when salt-tolerance plant was used to improve saline-alkali soil, we should use scientific measure to cultivation and management in consideration of requirement of different growth stages of forest for soil water and soil nutrient in order to consolidate the improving achievements and to accelerate the improving process.
Biological and biochemical properties in evaluation of forest soil quality